So cap space is needed only at the start of free agency?
That's not what I said. I said the only real risk I saw was underestimating the value of a top free agent. I don't believe any team would be caught so far off guard with the price of 2nd or 3rd tier free agents that they couldn't sign them. More to the point, any team that can't afford a 2nd or 3rd tier free agent outright is undoubtedly near the bottom of the league in terms of available cap space, which is likely a result of poor cap management in the first place. Almost 3/4ths of the league could acquire any player signed after week 1 of free agency right now. How many restructured every contract possible to get there?
Roster bonuses are not prorated.
So cut down on the base salary to maintain your space. Minimum salary and roster bonus a week later. Even with a $20M signing bonus, the cap charge would be at absolute most $5M if you applied a minimum salary for the short term. Restructure as needed and a roster bonus of whatever size doesn't hurt.
Teams already have plenty of flexibility to make things work in the short term. You don't need to prepare for something under the guise of flexibility when you already possess all the flexibility you need to operate.
There is nothing to "justify." Teams with cap space have the ability to improve their team in any way necessary, whenever the possibility arises. Teams without cap space either can't improve their team or have to delay the possibility long enough to create cap space. Someone calls with a trade offer during the draft? Nope, not enough time to create the cap room needed. Want to add a veteran after final cuts? Sorry, he signed with another team while you were busy trying to create enough cap room.
Sorry, but there is just no advantage and no point in not creating cap room.
Then answer the question as to why there isn't a single team that frees as much space as possible every offseason.
Signing a player you traded for or getting snaked by another team when it comes to signing a player......these would be exceptions, at best. The majority of the league could accommodate either move right now and they didn't get there through restructuring. This is beside the fact that the league offices actually close and all contracts must be league approved. Cap calculations aren't made the minute a player signs a contract, not officially anyway. Do you think league officials answer their phone in the middle of the night to look over transactions and give the okay? Additionally, what do you think, "agreement in principle", means to the NFL? Do they start calculating cap numbers with an agreement in principle even though the contract hasn't officially been submitted to the league and numbers are not available?
You're building barriers that simply don't exist. Like a doomsday prepper, you may as well be safeguarding against a giant solar flare that knocks out all electronic capabilities.
What if the fax machines I never knew were used were suddenly unavailable due to a giant solar storm? Then what would a team do?